Organic field effect transistors (OFETs) are used in display devices and logic capable circuits. A conventional OFET typically comprises source, drain and gate electrodes, an semiconducting layer comprising an organic semiconductor (OSC) material, and a gate insulator layer comprising a dielectric material.
For the preparation of a bottom gate device, usually the source and/or drain electrode layer comprising a metal or metal oxide is deposited onto a dielectric layer provided on a substrate. This is typically done by a sputtering process and subsequent lithographic etching process to remove unwanted areas.
Another conventional method of preparing a bottom gate OFET comprises the application of a patterned bank structure onto the dielectric and source/drain electrode layer, followed by deposition of an OSC layer, usually by inkjet printing, onto the bank structure, the dielectric and electrode layer. For the purpose of OSC layer positioning the surface of the bank structure is often subjected to a plasma treatment process before the OSC layer is applied, for example by exposure to a CF4 plasma or O2 plasma. CF4-plasma leads to a Teflon like, extreme hydrophobic surface (very low surface energy), which directs the inkjet drops not deposited accurately enough into the bank structure cavity.
However, it was observed that in the above-mentioned OFET preparation methods the electrode sputtering process and the plasma treatment process can cause significant damage on the exposed parts of the surface of the dielectric layer. As a result, the performance of device subjected to such a process is deteriorating.
It is therefore an aim of the present invention to provide an improved process for preparing electronic devices, in particular OFETs, which does not have the drawbacks of prior art methods and allows time-, cost- and material-effective production of electronic devices on large scale, especially with improved protection of the dielectric layer and other functional layers against plasma surface treatment techniques or plasma assisted deposition techniques that are applied during the device manufacturing process. Another aim of the invention is to provide improved electronic devices, especially OFETs, obtained by such a process. Other aims of the present invention are immediately evident to the expert from the following detailed description.
It was found that these aims can be achieved by providing methods, materials and devices as claimed in the present invention.